The present invention relates to a container of plastics material having preliminary folds, as well as to a process and a mould for the manufacture of a container of this kind.
More particularly, the invention relates to containers particularly intended for packing pulverous materials in bulk and in large quantities, thus having a considerable volume, e.g. of the order of 500-2000 liters.
It is obviously of advantage to be able to transport and store such containers folded, when they are empty, in view of the great amount of space which they occupy in use.
The numerous folding and packing systems at present known, using gussets or folded flaps, prove unsatisfactory in the case of this type of container because of the lack of flexibility in their walls, which have to be of sufficient thickness to provide good mechanical strength; this thickness may amount to about a millimeter.
A further method of reducing the space occupied by empty containers during their storage and transport would be to make them in several parts, to be welded together when the time came for their use, but this solution likewise proves unsatisfactory, as it results in potential rupturing points in the finished container.
As the container requires considerable mechanical strength, desirably combined with very limited wall thickness, the mechanical properties of the container must be homogenous, so that it must be manufactured in one single piece and folded subsequently, if it is desired to reduce the space occupied by it in storage and transport.
As the various folding systems at present known do not prove satisfactory, an object of the present invention is to provide a container so designed that it can be folded without difficulty, despite the thickness of its walls, as well as a manufacturing process for a container of this kind and a mould enabling the process to be applied. The blow moulding method is preferred.